I’VE had a month of strangers in my house. They sleep all day and at night have what sounds like very loud group sex in a confined space accompanied by prolonged shrieks of agony or ecstasy.

It always starts just a few minutes after I turn off the light. I creep out to turn on the light and find ... nothing.

Strange things happen. One morning the cutlery drainer was upended and the pot scourer was gone. Feijoas disappeared from an island bench. Passion fruit. Pears. Twice the strangers knocked all the objects off a window-sill five feet above the ground.

I suspected ringtail possums, but why did I never see them? There were no droppings anywhere. Were they living in the wall? How did they get out of the wall and into the room? And how did they climb onto an island bench with an overhang?

I grew hollow-eyed, jumpy and irritable, especially with my ancient deaf cat, who slept through the racket.

Once night when my visitors had woken me with their thumping and crashing, I turned on the light and saw a very long tail poking out from behind the fridge, motionless.

Rats. Not living under my house, or even in the roof, but living in my house. One of our primal fears. George Orwell had rats bring Winston Smith undone in 1984.

The next morning, I gingerly pulled out the fridge, expecting a family of 12 to rush in all directions. There was nothing there! Well, no living thing, but a nest of chewed up sponges, the missing pot scourer and a heavy rubber brush. The walls, floor and bottom of the fridge were spattered with poop, pee and the remains of fruit and cat’s biscuits.

When I went to the hardware store to buy a rat trap, the man said “They’ve been walking out the door”. I thought he was saying it to make me feel less ashamed of having rats in my house until we got to the rat trap shelf and it was empty. At the second store, there were only two traps left, big heavy plastic things that cost $9 each, and I grabbed them both.

That night I set the traps beside the fridge. Ten minutes after I turned off the light, the first went off, waking me with a start. The second one went off about 2am, followed by the sound of an animal thrashing around in pain. It stopped after about 20 seconds and I guessed it was dead. In the morning there were two sprung traps and one very big dead rat. I buried the rat and hoped the others would take heed and leave.

When I told my friend Vilya about my kill, she asked if it was a bush rat, which complicated the matter. Sewer rats spread the Black Plague but bush rats are native and cute. It would be like killing an Easter bilby. Last winter a family of bush rats lived in my compost bin and we cohabited quite happily.

I went home and looked up rats on the Museum Victoria site. It said Rattus rattus, the black rat (which is actually brown or grey), has pointed ears and long tails, while bush rats have rounded ears and tales shorter than their body length.

But behaviour was the telling point. “Bush rats are shy. They rarely enter buildings and are usually found well away from human habitation. They do not construct nests in buildings. Black Rats, on the other hand, love to nest in buildings.”

I also learned that rats are among the most intelligent and altruistic of animals. Wish I hadn’t read that. But when I emailed my friend Ann, she replied “Rattus rattus are nasty wee buggers. Fight on. Mike saw one standing on its back legs fighting the cat recently.”

So I set the traps again that night. At least it’s better than poisoning them. Ten minutes after I put out the light, there was a crash. Then thrashing. I counted to 20, then to 20 again and still it went on. After five minutes, I went out to confront my worst nightmare. The rat was caught around the neck. I used the kitchen tongs to pick up the bloodied trap, took it outside, opened the trap and the rat hobbled off into the blackness. “Don’t come back,” I called, then went inside and vomited.

The ancient cat appeared, making strange rumbling noises. Was she dying or had the smell of rat blood awakened an ancient bloodlust? God, I was over Nature.

But the rats were quieter now. I seemed to have caught the loudest, brashest ones first. Now I was dealing with the quiet, canny ones. I reset the trap the next night and lay awake tensely waiting for the crash. Nothing happened and eventually I drifted off. In the morning there were the remains of a feijoa on the floor. Clearly the survivors were quick learners and were avoiding the traps.

The next morning it was a lemon. The avocado the next day was the last straw. Right. This was war. I hid everything vaguely edible and reset the traps with apricot jam and cheese.

In the morning, a juggling ball was on the floor, split open with half the wheat gone.

Last night I put the juggling balls in a cupboard, along with a woven flax dish. I hid the onions. I was fast asleep when the trap went off and I heard an animal thrashing about. This time I was up quickly. It looked like Granddad Rat. I took him outside and opened the trap and he scuttled away. Then I went back to sleep, which shows how quickly we adjust to appalling things.